1. Field of the Invention
The present invention relates to a composite packing film and a packing bag or pouch made of the composite packing film, and particularly to a composite packing film suited for packing relatively heavy materials including foodstuffs and medicines, such as soft drinks, seasonings, flavorings and chemicals.
2. Prior Art
A variety of composite packing or wrapping films have been proposed in recent years to meet different requirements for packing or wrapping goods having various properties, and the development of such composite packing or wrapping films has contributed to improvements in the field of package technology. However, the endeavours hitherto expended for the development of composite films have been directed primarily to the improvement in package making technique, such as improvement in processing of the packages or sealing property of the film, and to the improvement in preservation of the qualities of the goods which are packed by the composite films. As a result, only a few efforts have been made to investigate the tearing property and the orientation of the cut line when the bag or pouch is opened. Subsequently, the conventional composite packing or wrapping films are unsatisfactory in this respect.
As has been well known, the packing bags made of composite films are generally handled and processed by automatic machines, and the tearing property and the orientation of cut line of the bags at the opening operation tend to be ignored or neglected. However, the bags are generally opened by the hands of the consumers to gain access to the goods contained therein. In consideration of the convenience for the consumers, it is highly desirous that the film be easily torn. Particularly when the film is used to form a pouch for packing food stuffs, medicines or the like materials, it is of significant importance that the film be easily torn to open the pouch individually by the fingers of the consumers. In addition to the tearing property as aforementioned, it is also desirous that the packing pouch or bag can be torn or cut linearly along a predetermined direction. In the case where a liquid, powdered or granular material is contained in the pouch or bag, if the cut line is not determined and the pouch or bag is occasionally torn diagonally or in a zigzag form, there is a fear that the contained material will be spilled or run out and expending of care is thus necessitated to open the pouch or bag made of the conventional composite films.
In order to overcome the aforementioned disadvantage of the pouch or bag made of the conventional composite film, we have proposed composite films and packages made of the same by Japanese patent application No. 88936/1978 (Japanese Patent Provisional Publication No. 15839/1980) and Japanese patent application No. 17803/1979. However, although the composite films of this type, wherein the tearing property mainly depends on the orientation of molecules in the unidirectionally elongated film, have sufficient strength along the elongated direction, the strength thereof along the direction transverse to the elongated direction is not satisfactory and cannot be used for packing relatively heavy materials.